1. Field of the Invention
The present invention relates to a disk drive seek control system, and more particularly to a disk drive seek control system to reduce track pitch.
2. Description of Related Art
Developments in manufacturing and control technology have significantly increased the recording density of disk drives. The high recording density makes the magnetized region per unit signal recording narrower and narrower. Conventional methods of reading signals using the relative movement between a conventional magnetic head and a magnetized region on a recording disk have almost reached their technical limit. Accordingly, a method of reading signals using a MR (Magneto-resisitive) head which utilizes the magneto-resistive effect but does not directly use the relative movement between a head and a disk is now in use.
Since this MR head is a read only head, disk drive read/write heads include a separate conventional magnetic head for writing. FIG. 2 shows a plane view illustrating the structure of such a read/write head using a MR element. In such a read/write head x1, there is an offset between a read head element (a MR head) x2 and a write head element (a conventional magnetic head) x3 due to its structural characteristics.
In a Winchester type hard disk drive, a rotary actuator is generally used for positioning a read/write head in a transversal direction of the tracks. As shown in FIG. 3, the center line of the read/write head x1 has a yaw angle (xcex81, xcex82) with respect to the track center line. This yaw angle varies with the rotational angle xcfx81 (a skew angle) of the rotary actuator.
The read/write head x1 composed of the read head element x2 and the write head element x3 with an offset as shown FIG. 2 is mounted on the rotary actuator so that the centers of the read and write head elements x2 and x3 are in line with the rotational center C of the rotary actuator as shown in FIG. 3. Accordingly, as shown in FIG. 4, the position difference xcex94w (xcex94w=L sin xcex8) is generated between the read and write head elements x2 and x3 in the radial direction of a track depending upon the yaw angle xcex8 of the read/write head. This position difference xcex94w does not cause a big problem and is negligible when this difference is relatively small compared to the track width. However, as track widths have become smaller, the position difference xcex94w has become increasingly large and is no longer negligible. When GMR (Giant Magneto-resistive) heads of spin valve type are used instead of a MR head, the offset (L) is even larger than that of the MR head. Therefore, the position difference is also larger.
In order to increase the accuracy of the positioning of the head x1, for instance, the read head element x2 reads the servo signal recorded with a predetermined angle space on a track to detect the exact position of the head x1 and then controls the positioning of the head x1 based on the detected position. However, even if the position of the head x1 is so accurately controlled, it is very difficult to reduce track pitch further because of the variance of the recording position of the write head element x3 caused by the offset xcex94w corresponding to the yaw angle.
Accordingly, it is an object of the present invention to provide a disk drive apparatus and a seek control device thereof which further reduce track pitch so as to increase recording density.
The present invention provides a disk drive seek control system to reduce track pitch. A disk drive apparatus according to the present invention includes a disk-shaped recording medium with a plurality of concentric tracks thereon. Each track has a servo pattern recorded on it for the purpose of tracking control. A head actuator module in the disk drive has a read head element and a write head element. The head actuator module moves the read head element and the write head element in a transverse direction across the tracks. The head actuator module separately positions the read head element and the write head element in the radial direction of the tracks, with an offset which varies with a skew angle of the head actuator module. A position detection module in the disk drive detects a position of the read head element from a readout signal of the servo pattern read by the read head element, and outputs a position detection signal. A servo control module controls the head actuator module based upon the position detection signal. An offset detection module detects the offset between the read and write head elements in the radial direction of the track according to the skew angle, and outputs an offset detection signal. The disk drive further includes a write head element position compensation module which based on the offset detection signal, controls the servo control module so as to position the write head element at a predetermined position along the radial direction of a first predetermined track during write operations.
The disk drive apparatus of the present invention further comprises a seek control device for positioning a read/write head at a predetermined track on a disk-shaped recording medium. The disk-shaped recording medium is provided with a plurality of concentric tracks on which a servo pattern is recorded for the purpose of tracking control. The seek control device includes a position detection module, a position control module and a seek completion detection module. The position detection module reads the servo pattern, and for each readout of the servo pattern, outputs position detection signal which has a nonlinear characteristic with respect to the displacement of the head in the track. The position control module moves the read/write head to a target position based upon the position detection signal.
The seek completion detection module determines when the seek operation is complete. When the variance of the position detection signal from the position detection module, corresponding to the displacement of the head at the target position, is relatively small, the seek completion detection module checks the position detection signal to determine whether the position detection signal shows, for a first predetermined number of times, that the head is within a first region from the target position. The seek completion detection module then checks the position detection signal to determine whether it shows for a second predetermined number of times that the head is within a second region from the target position which is closer to the target position than the first region. Next, the seek completion detection module checks whether the variance of the position detection signal is within a first range over a first time period. If the above conditions are all true, then the seek operation is determined to be complete.
Other objects, features, and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description below.